The spray painting of automobile bodies, truck engines, appliances and other industrial goods is customarily carried out in enclosed areas called paint spray booths (PSB). These booths act to contain solvent fumes and oversprayed paint and to reduce the chances of dust, contamination in order to protect the paint booth operators. These booths vary in size, but are somewhat basic in their design and operation. A typical booth would thus consist of a work area, back section with mist eliminators and a sump.
The units to be painted generally pass through the work area while an air flow makes the oversprayed paint contact either the sump water or the spray from the water curtain. The air is scrubbed with recirculated water at the water curtain, passes through the mist eliminators and is removed by an exhaust fan.
Even though paint transfer efficiencies have increased through improved application technologies, roughly one-half of all paint sprayed does not reach its intended article. As a result, a significant concentration of paint builds in the system and agglomeration can occur. The resultant mass is a sticky, tacky material which can plug the mist eliminators, shower heads and even recirculating pumps. When this happens, scrubbing efficiency decreases leading to potentially hazardous conditions of unchecked paint emissions being discharged into the atmosphere. Such conditions may also present severe safety hazards to paint spray booth operators.
These tacky organic deposits are subject to bacterial growth and the proliferation of fungi. These conditions generate corrosion and odor problems. In addition, the paint solids that are recirculated can form suspensions in the water which remain tacky and can create expensive separation and disposal problems.
These problems show, therefore, the desirability to treat PSB water systems so as to reduce or prevent as much as possible the agglomeration and deposition of oversprayed paint on critical PSB operating parts, to render the resultant sludge non-tacky and easily removable and to provide a water quality such that it can be recycled for use in the system.
Numerous paint detackification programs are known. Some paint spray booth operations utilize an activator catalyzed detackification program (ACDP). Within ACDP technology, an anionic species, such as a silicate, activates, or catalyzes, a cationic organic polymer. The activated organic polymer detackifies oversprayed paint particles present in the wash water. Problems arise, however, with the excessive loss of the activator species as a precipitate due to the common occurrence of increasing acidification of the wash water.